Which of the following is a life-threatening shockable arrhythmia?

Ventricular Fibrillation is identified as a life-threatening shockable arrhythmia due to the chaotic electrical activity that disrupts the normal rhythm of the heart. In this condition, the heart's ventricles quiver ineffectively instead of contracting properly, which prevents blood from being pumped to the body and brain. This lack of blood flow can quickly lead to death if not treated swiftly. The primary treatment for ventricular fibrillation is defibrillation, which involves delivering an electrical shock to the heart to restore a normal rhythm.

In contrast, the other arrhythmias listed, such as Atrial Fibrillation, Sinus Tachycardia, and Bradycardia, either do not require immediate electrical intervention or are not classified as shockable. Atrial Fibrillation may cause complications but is treated differently, and while Bradycardia can be serious, it's typically managed with medications or pacing rather than defibrillation. Sinus Tachycardia is often a compensatory response to various physiological conditions and is not inherently life-threatening in the absence of other conditions. Thus, the distinction of ventricular fibrillation as a shockable rhythm is vital for effective emergency response in the context of cardiac arrest.